1. Field of the Invention
The present invention relates to a method of producing a nozzle plate including nozzle holes for ejecting an ink, and also to such a nozzle plate.
2. Description of the Related Art
An ink jet head includes a nozzle plate having many nozzle holes, and is configured so that an ink is ejected from the many nozzle holes onto a recording medium. An example of such a nozzle plate is a nozzle plate 100 in which, as shown in FIG. 16, a nozzle hole 102 having an inner face of a tapered shape is formed in a substrate 101 made of polyimide or the like by excimer laser processing or another method.
In another nozzle plate 110, as shown in FIG. 17, a nozzle hole 112 is formed in a metal substrate 111 by press working using a punch or the like. The nozzle hole is formed of: a tapered hole portion 112a which is continuous to an ink flow path on an upstream side, and which has a truncated conical shape; and a columnar hole portion 112b which elongates from the smallest diameter end portion of the tapered hole portion 112a to an ink ejection port 113 in the surface of the substrate 111. However, in the nozzle hole 112, the rate of change of the inner diameter is very large in a portion where the tapered hole portion 112a is connected to the columnar hole portion 112b, thereby causing the possibility that the property of ink ejection from the ink ejection port 113 (particularly, the ink impact accuracy) is adversely affected. Therefore, a nozzle plate 120 shown in FIG. 18 has been proposed in which a nozzle hole 122 having: a tapered hole portion 122a; a columnar hole portion 122b; and a curved-surface hole portion 122c that smoothly interconnects the tapered hole portion 122a and the columnar hole portion 122b and that has an arcuate section shape is formed in a substrate 121 (for example, see U.S. Pat. No. 6,170,934 (columns 6 and 7; and FIGS. 3A and 3B)).
In the case where nozzle holes are formed in a substrate by excimer laser processing, press working, or another method, it is usual to remove the surface of the substrate by polishing or the like in order to eliminate burrs and swelling formed in the surface of the substrate.